The dancer at the Silver Slipper - the downtown strip club here that Wilbur Mills and Fanne Foxe made famous - smiled at the ringside customer as she undressed on stage. Afterwards, she asked him if he wanted her company, suggested that he buy a bottle of champagne, and led him to a dark rear booth.

The bottle of Franzia champagne ($1.80 wholesale), for which the customer was charged $35 plus tax, was soon empty, much of it going into a green plastic "spit cup" alongside the dancer's glass.

Offering the customer mints from inside the top of her scanty costume, the dancer asked him to buy another $35 bottle. When he refused, explaining that he was out of money, she told him she could not sit with him any longer.

"I have a six-bottle quota tonight," she told him."What we do here is illegal, you know," she added. "We're not supposed to solicit drinks from customers."

But she did it anyway, she said, because in addition to her $300 weekly salary for dancing, she received commission for the drinks she persuaded customers to buy at very high prices.

These commissions at the Silver Slipper, sources have told The Washington Post, range from 50 cents on a $3.80 cocktail to the $80 commission a dancer receives if she persuades a customer to pay $600 for an eight-quart "Methusala." In this way, according to records, reviewed by The Post, Siler Slipper customers have been persuaded to run up bills of hundreds and even thousands of dollars each in a single night.

The Silver Slipper's manager, Tom Latimer, denied all this. "Dancers don't solicit drinks or get commissions," he said in an interview. "We have advised, informed and demanded that the girls act in a superb manner at all times. They are told they'll be fired if they solicit for anything."

But, according to sources inside the club business, law enforcement officers and records of the D.C. Alcoholic Beverage Control Board, such practices are common at several downtown strip clubs like the Silver Slipper, which cater to businessmen and government officials with money.

Among the rest of the 50 establishments featuring nearly or completely nude dancers in Washington are also office district restaurants that provide topless dancing along with corn beef and quiche for their mostly white collar patrons and neighborhood go-go bars where students and blue collar workers drink cheap beer and watch completely nude, or "bottomless," dancers perform.

At all of these places, sex is the primary attraction for customers.

The sexual lure is most blatant at places like the Fantasy Lounge on 11th Street NW near Pennsylvania Avenue. To watch the "8 Very Foxy Ladies" advertised on a sign in the front window, a customer goes through a tassled curtain at the back of the front grill room to a stage and bar where beer is served at $1.65 a glass and nude women perform dances that include simulated sex with the customers.

On a recent afternoon, to the beat of jukebox music for which she had solicited quarters, a nude dancer climbed onto a customer's table and nuzzled her body against him. Then she turned to another customer, a tourist with two cameras, and asked, "Want some?"

Sex at the Silver Slipper is more subtle and much more expensive.

"Basically, the girls give the customers as little as they can get away with in terms of sex," said a former Silver Slipper waitress. "When a man buys a bottle and moves into the back, he thinks he's going to get something. Sometimes, they'll promise or give the man the impression they're going to leave with him. In the meantime, they'll try to get him for as many bottles as they can get . . . They do everything back there except actually go to bed."

In the process, big bills are run up. Customers who agree under strong encouragement to use credit cards often find their bills far higher than they imagined possible.

One high-ranking federal government employee was listed in Silver Slipper records reviewed by The Post as spending, $4,200 on a single night at the club last November. According to the waitress who served the customer, he was charged for 50 bottles of champagne that he and his dancer companion supposedly consumed.

In an interview with The Post, the customer, who did not want to be identified, said he also lost his American Express credit card and reported it missing. But he still received a credit card bill containing $1,700 in Silver Slipped charges, which, he said, "shocked me out of my wits."

Washington police officers say they frequently receive anguished telephone calls, many of them long-distance, from customers of the Silver Slipper and other strip clubs here compaining about enormous credit debts. But none are willing to testify publicly about it.

Over the years, under different owners, the Silver Slipper has repeatedly been cited by the ABC Board and by police for solicitation of liquor purchases and, upon occasion, for prostitution. All of this has resulted in periodic license suspensions, and, in some cases, criminal charges against some employees.

Keeping tabs on such operations "is not an important mission within the police department," said one Washington officer. "It doesn't fit anywhere on a scale of one to 10." The ABC Board is incapable of enforcing its own rules, which prohibit much of what goes on in the girls-and-alcohol establishments, because of insuffient funds and staff, according to ABC Board officials.

Just in case, however, the strip clubs maintain their own security. One 14th Street NW club, according to a former waitress, places a bar towel in front of a customer suspected of being a police officer. At the Silver Slipper, according to the former waitress, the suspicious person receives a gold rather than black ash tray.

Within minutes of being seated at the Silver Slipper on a recent winter evening, a customer was asked by a robed dancer, "Would you like some company?" She was in her early 20s, with heavy eye makeup. During the day, she said, she was studying art and fashion design at a suburban college.

After a while, the dancer said she would have to leave unless the customer bought her a drink because that was the house rule.

Then another dancer sat down. She and the waitress urged the customer to use his credit card to pay for drinks. His wife would never know, they assured him, because the charge would read "Royal Restaurant, Inc."

Ownership of the Silver Slipper passed from Silver Slipper, Inc., to Royal Restaurant, Inc., in 1973. ABC rules require public disclosure of persons owning 25 per cent or more of a club, but the license transfer and renewal forms do not contain the information.

ABC investigative files include a photostatic copy of a stock certificate in the name of Ingram T. Benson, "trustee." The actual owner, according to a handwritten note in the file, is Robert F. Koch, a Bethesda builder of apartment houses and shopping centers.

Nic Trotta, whose real name is August Nicholas Magliano, is listed as corporate treasurer on the Slipper's pending license renewal application Trotta, with his late brother, Benny, owned the Club Troc on Baltimore's "Block" of strip clubs from 1952 until its sale and conversion into an adult book store in 1976.

Trotta, a former amateur boxer with receding silver gray hair and wearing a white open-necked shirt and pin-striped suit, insisted his dancers do not received commissions for drinks sold.

"A lot try to (talk) a customer out of his money by crying the blues," he said. "Soliciting for prostitution is against my rules and regulations. A lot of girls, they do a lot of things, you know. It's against the policy, but you need girls, you know.

"Dope I won't put up with," he said. "If an owner is in with a girl and takes her money while she's prostituting . . . I don't want no parts of it, either."

"Our customers don't come here to relax, to be entertained, to unwind, not for sex."

Trotta, who said he may in the future acquire the Silver Slipper, for which he now only works, and Latimer, his partner, said their desire is to upgrade the establishment, sell more food, and, at least once a month, attract respectable middle-aged couples with well-known entertainers. Already, they said, George Jessel appeared there for a week over the New Year's holiday, and they have high hopes for other big names in 1978.

"If I'm looking to run strictly a joint and this and that, I wouldn't bring them in," Trotta said. "Let's put it this way, we're trying. We even got all brand new utensils for the buffet."